In the conventional pneumatic tools the techniques of regulating the rotation speed of the rotor in the air chamber by controlling airflow are known in art. They mostly use a valve lever to control the airflow entering the air chamber. The mechanism generally is formed with a special shape. Hence it is difficult to maintain a consistent quality during manufacturing, and the accuracy to regulate the airflow is affected.
There is another type of control mechanism to regulate the rotation speed of the pneumatic tools that adjusts the size of the air inlet through different sizes of ports. The ports are formed on an airflow knob may be used to achieve different rotation speeds of the rotor. The sizes of the ports are preset. Hence the rotation speed of the rotor is limited to a preset range and cannot offer a stepless regulation. All these hinder the use effectiveness of the pneumatic tools.